Road Trip
From Halopedia, the Halo wiki
Road Trip is a medal awarded in Halo 4 multiplayer and Spartan Ops. The requirements for the medal are somewhat unclear, as the medal's description in-game differs from its description on Halo Waypoint. On Halo Waypoint the medal is described as: "Load up a Warthog with 2 teammates and go for a drive." This suggests players need only drive a Warthog with two passengers in order to unlock the medal.
In-game however, the description reads: "Load up a Warthog or mongoose with teammates and splatter an enemy player." This allows the player to use a mongoose, but also requires that the player splatter an enemy. The fact that the medal is awarded in Spartan Ops would indicate that the term "enemy player" actually applies to AI enemies as well.
The fact that the medal is only typically awarded once per Spartan Ops match, regardless of the number of splatters scored by the player, would suggest that the Waypoint description is the more accurate.